Study on thermally conductive ESBR vulcanizates

Abstract

The thermal conductivities of emulsion polymerized styrene-butadiene rubber (ESBR) vulcanizates filled with alumina (Al2O3), zinc oxide (ZnO), carbon nanotubes (CNTs), silicon carbide (SiC), are measured by steady-state method. The effects of types and loadings of the fillers and their mixture on thermal conductivities of the ESBR vulcanizates are investigated. The results show that the thermal conductivity of ESBR vulcanizates filled with alumina or zinc oxide, increases nearly linearly with increasing loading when the filler loading exceeded 20 phr; the ESBR vulcanizates filled with CNTs have the highest thermal conductivity at a given filler loading in comparison with other composite vulcanizates. At a given loading of 100 phr, the ESBR vulcanizate filled with two different particle sizes SiC of 1–3 and 5–11 μm at the mass ratio of 1:1 has the highest thermal conductivity and relatively good mechanical properties. The experimental results are analyzed using Geometric mean model and Agari’s equation to explain the effect of filler types and particle sizes on the formation of thermal conductive networks. The thermal conductivity of the ESBR vulcanizates filled with Al2O3 or ZnO or CNTs could be well predicted by optimized parameters using Agari’s equation for a polymer composite filled with mixtures of particles.